In a fresh install of 11.04 Natty, Japanese characters (Kanji, some Kana) were still not displaying correctly in URLs and after I followed the instructions for installing Japanese language support. URLS, for example, were still displaying as boxes. This was regardless of whether I was using an English or Japanese session.
My workaround was to set the system/app/desktop fonts in Appearance to the 'Takao' fonts.
However, this feels suboptimal--I remember just displaying East Asian languages being much easier in the past. What's the deal? Do the fonts packaged with Natty (Ubuntu, Sans et al.) no longer support East Asian languages like Japanese?